I am a big fan of color restrictions, since it rewards you for playing a certain deck. The problem isnt with Lost Dragon, its the fact that some cards dont have this restriction and are thus superior. If anything we should be looking at this, instead of removing it. There is a reason deepone was 1G but changed to GG. Same with War Eagle. I know you are making a case for Tier 4, but I dont think the logic is much different. You want to be rewarded for going all in on a certain combination. Enligtenment goes arround this (which is why I dislike it in general), but that at least forces you into GG, making your Tier 1 and Tier 2 be effected by your choices.
So if you want to play harvester and lost dragon, you now have to go SSFF or SSGG (with enligtenment on tier 4 to cheat it out). This is a good thing. You are now rewarded for playing Lost Souls and get the Lost Dragon on tier 4, while also playing something that Enligtenment decks could not (Harvester on tier 2).
The problem arises with less restrictions like Lost Spirit ship, cause its arguably just better to go nature. Then again, people need to stop thinking of this game as people-will-only-play-the-very-best-deck, and also consider the casual players who just want to play cool stuff and feel rewarded for their color combinations.